Mixed reality devices allow users to view the real world while simultaneously viewing computer generated graphics overlaying real world objects and scenery in the user's field of vision. These graphics may be used by the device to enhance the user's viewing experience in many ways, such as by displaying information about objects or locations viewed by the user.
Common designs for mixed reality devices utilize reflective beamsplitters and mirrors to direct both ambient light from the real world and light from an electronic display device toward a user's eye. In a typical design, ambient light enters the device through one beamsplitter while light from an electronic display enters through a second beamsplitter. Light from each source travels along separate light paths before being overlaid and directed out of the system toward the user's eye. In order to properly direct the light, however, the light paths within the system often require the light to pass through or reflect from the first or second beamsplitter one or more times.
Reflective beamsplitters are typically designed to transmit or reflect only a portion of incident light. Thus, mixed reality devices are severely limited by the amount of light intensity lost each time the light in the system reflects from or is transmitted through one of the beamsplitters. As a result, the brightness of the light in the system is diminished and the contrast between the ambient light entering the system and the light generated from the electronic display device cannot be properly controlled. Such an effect reduces the sharpness of graphics displayed on the device and negatively impacts the user's viewing experience. In addition, the loss of light from the electronic display requires the device to expend more power to produce visible graphics and thus reduces the overall battery life of the device.